The present invention relates to a wear-resistant coating which exhibits properties of low-friction, low-clogging and resistance against static electricity. The invention relates further to a process for forming the coating and products utilizing same.
The aforementioned type coatings are generally formed over surfaces which are prone to wear, scratching, collecting of debris and formation of static electricity due to exposure to an external rubbing action. Magnetic recording media sensors (MRMS) which may be used for reading and/or writing of magnetically stored information are typical examples of such surfaces.
Coatings which have been recently developed are suitable for use in hard disc and floppy-disc reading/writing heads, video and audio heads, magnetic discs and magnetic tapes, magnetic counters, etc. As an MRMS operates in close and/or direct contact with other MRMS surfaces, debris and abrasive particles move relative thereto.
In accordance with conventional practice, the MRMS and its surface are coated by a protective film which includes at least two layers having different hardness and electrical conductivity. Moreover, such film is coated by means of chemical vapor deposition (CVD) with heating assistance. Due to such heating assistance, deformation of substrate and creation of inner stress is unavoidable, and the performance of the particular MRMS is consequently decreased. The external surface of the coating has a higher degree of hardness for providing an abrasion-proof surface, and the inner layer has comparatively low resistivity in order to abate the influence of static electricity. However, the use of multilayered film increases the coating thickness and/or decreases its wear resistance, and increases the production cost.
Accordingly, it is an object of the invention to provide an effective abrasion-proof, low-friction, low-clogging, static electricity erasing, thin film coating method.
It is a further object of the invention to provide an apparatus for forming such thin film coating which inhibits damage of the MRMS even when operating in close or direct contact with other MRMS surfaces, and in the presence of debris and abrasive particles moving relative thereto, even at low temperatures.
In accordance with these and other objects of the invention, an MRMS is coated directly with hard amorphous carbon (also referred to herein by the term xe2x80x9cdiamond-like carbonxe2x80x9d or DLC) films having a high degree of hardness, smooth surface and low friction coefficient, to provide an abrasion-proof surface, which significantly abates the influence of static electricity and which collects a minimum amount of debris. These properties can be realized using vacuum pulse arc carbon sputtering and ion beam surface treatments. For purposes herein, the term xe2x80x9cMRMSxe2x80x9d will refer not only to the magnetic recording media sensor itself, but also alternatively to the media used with such sensor.
According to a preferred embodiment of the present invention, the content of sp3-bonded carbon (hereinafter sometimes referred to as xe2x80x9csp3xe2x80x9d) in the coating is within the range of about 30 to about 85 percent. The Vickers hardness is in the range of about 3000 to about 9000 kg/mm2. The deposition process advantageously employs ion beams, and the coating process may be done with repetition of deposition and etching using such ion beams. Further, the beams may be scanned. One or more substrate holders are advantageously provided in a location in the deposition chamber out of projections of the ion and carbon sources in the direction of gravity, an electrical resistance of the substrate holder or holders to earth junction being set in a range of about 1 Mxcexa9 to about 10 Mxcexa9.